Title: A New Pocket Gopher (Thomomys) and A New Spiny Pocket Mouse (Liomys) from Michoacán, Mexico
Author: Hall, E. Raymond (Eugene Raymond), 1902-1986, Villa Ramírez, Bernardo, 1911-
Language: English
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*** Start of this LibraryBlog Digital Book "A New Pocket Gopher (Thomomys) and A New Spiny Pocket Mouse (Liomys) from Michoacán, Mexico" ***


               A New Pocket Gopher (Thomomys) and A New
                   Spiny Pocket Mouse (Liomys) from
                          Michoacán, Mexico

                                  BY

                E. RAYMOND HALL AND BERNARDO VILLA R.


                  University of Kansas Publications
                      Museum of Natural History

            Volume 1, No. 14, pp. 249-256, 6 figs. in text
                            July 26, 1948


                         University of Kansas
                               LAWRENCE
                                 1948



     UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

        Editors: E. Raymond Hall, Chairman; A. Byron Leonard,
                           Edward H. Taylor

            Volume 1, No. 14, pp. 249-256, 6 figs. in text
                            July 26, 1948


                         UNIVERSITY OF KANSAS
                           Lawrence, Kansas


                              PRINTED BY
                   FERD VOILAND, JR., STATE PRINTER
                            TOPEKA, KANSAS
                                 1948

                               22-3338



            A New Pocket Gopher (Thomomys) and a New Spiny
             Pocket Mouse (Liomys) from Michoacán, Mexico

                                  By

                E. RAYMOND HALL and BERNARDO VILLA R.


A series of 17 pocket gophers of the species _Thomomys umbrinus_
obtained in 1943 from points 3, 4 and 5 miles south of Pátzcuaro proves
upon comparison to be an hitherto unrecognized subspecies which is
described and named as follows:

              #Thomomys umbrinus pullus#, new subspecies

    _Type._--Male, adult, skin and skull; No. 100151, Univ.
    California Mus. Vert. Zool.; 5 mi. S Pátzcuaro, 7800 ft.,
    Michoacán, Mexico; March 10, 1943; obtained by Hubert H. Hall,
    original No. 117.

    _Range._--Known only from 3 to 5 miles south of Pátzcuaro,
    Michoacán.

    _Diagnosis._--Size small (see measurements); color black or
    between Cinnamon-Brown and Snuff Brown; distal half of tail
    whitish and all of tail whitish in one specimen; lambdoidal
    crests perpendicular to sagittal plane of skull; posteroventral
    face of tympanic bulla rugose; jugal vertical (flat surface not
    oblique); interpterygoid space truncate at apex with sides
    curved outward (see figure).

    _Comparison._--From topotypes of _Thomomys umbrinus supernus_
    Nelson and Goldman, _pullus_ differs as follows: More
    individuals wholly black (except distal half of tail);
    underparts lacking white; rostrum broader; braincase anteriorly
    slightly more expanded dorsally; lambdoidal crests perpendicular
    to sagittal plane rather than inclined posteromediad;
    interparietal broader, [Male] 5.7 (5.0-7.0) versus 4.5, and in
    [Female] 6.5 (5.6-7.1) rather than 4.8 (4.4-5.1); flattened
    middle part of jugal vertical rather than oblique; in side view,
    mastoid and paroccipital processes farther apart thus exposing
    larger surface of mastoidal bulla; incisors, in both upper and
    lower jaws, slightly narrower; molariform teeth smaller,
    interpterygoid space truncate, at apex, with sides convex
    mediad, rather than V-shaped; ventral face of tympanic bullae
    rugose in posterior half rather than smooth.

[Illustration: FIGS. 1-3. Three views of the skull of the type specimen
of _Thomomys umbrinus pullus_. × 1.]

_Remarks._--Among named subspecies of _Thomomys umbrinus_, _T. u.
pullus_ most closely resembles _T. u. supernus_, the subspecies next
adjacent to the northward. Therefore, the results of comparisons with
only that subspecies are here reported upon. _T. u. tolucae_ to the
eastward is for one thing a much larger animal and has slightly less
procumbent upper incisors. So far as we know, _Thomomys umbrinus_ has
not heretofore been reported from Michoacán. Of our seventeen skins,
eight are brown, six are black and two are intermediate in color.

Most of these pocket gophers lived where there was a good growth of pine
trees in the same areas where large pocket gophers of the species
_Cratogeomys gymnurus_ occurred. The field notes of the collector of the
type of _T. u. pullus_ record that when he was making a shallow
excavation to reveal the gopher burrow in which he trapped the holotype,
he found the burrow approximately five inches below the surface of the
ground and that in digging deeper than was necessary he accidentally
broke into the burrow of a _Cratogeomys_. Another member of our field
party (E. R. Hall) when removing from its burrow a trapped _Thomomys_
that was caught only by the hind leg, dug around the animal whose burrow
was approximately six inches underground and in doing so he also broke
through the roof of a burrow of _Cratogeomys_. The burrow of
_Cratogeomys_ was approximately sixteen inches below the ground. Nowhere
else, except 3 to 5 miles south of Pátzcuaro, have the authors found two
kinds of pocket gophers living together. The two-story arrangement south
of Pátzcuaro was possible because of the different levels at which the
two kinds of animals made their burrows and the two-story arrangement
was accidental and exceptional rather than the rule.

    _Measurements._--Average and extreme measurements of five adults
    of each sex, are as follows: Total length, male 184 (178-198),
    female 185 (174-194); length of tail, 54 (48-60), 53 (47-57);
    length of hind foot, 26.8 (25-29), 27.6 (26-29); weight, 86.1
    (78.7-96.9), 74.3 (70.2-84.8) grams; basilar length, 30.2
    (28.8-31.3), 28.6 (27.8-29.1); zygomatic breadth, 23.2
    (22.3-24.6), 21.3 (20.8-21.8); least interorbital breadth, 5.9
    (5.8-6.1), 6.4 (6.0-6.8); mastoid breadth, 17.8 (17.1-18.7),
    17.2 (16.6-17.5); length of nasals, 12.4 (11.8-13.0), 11.5
    (11.0-12.5); breadth of rostrum, 7.5 (6.9-8.2), 7.1 (6.9-7.3);
    length of rostrum, 14.1 (13.4-14.5), 13.3 (12.7-13.5); alveolar
    length of maxillary tooth-row, 7.0 (6.7-7.5), 6.9 (6.8-7.0);
    palato-frontal depth, 13.2 (13.0-13.4), 12.9 (12.3-13.5).

    _Specimens examined._--Total, 17, all from 7800 ft., Michoacán,
    as follows: 3 mi. S Pátzcuaro, 1; 4 mi. S Pátzcuaro, 10; 5 mi. S
    Pátzcuaro, 6.

       *       *       *       *       *

In 1943 a series of fifteen spiny pocket mice, _Liomys irroratus_, was
obtained within a radius of five miles of Pátzcuaro and, mostly on
geographic considerations, the animals were assigned to _Liomys
irroratus alleni_ (Coues). In fact, in his "Revision of the Spiny Pocket
Mice," Goldman (N. Amer. Fauna, 34:57, 1911) had thus identified the one
specimen available to him from Pátzcuaro. Critical examination of the
series, however, revealed cranial features not described in the named
kinds from adjoining geographic areas, and comparisons showed that the
animal from Pátzcuaro differs subspecifically from any named kind. The
new subspecies may be known as:

              #Liomys irroratus acutus#, new subspecies

    _Type._--Female, adult, skin and skull; No. 100171, Univ.
    California Mus. Vert. Zool.; 2 mi. W. Pátzcuaro, 7700 ft.,
    Michoacán, Mexico; March 10, 1943; obtained by E. R. Hall and J.
    R. Alcorn, original No. 3837 of Alcorn.

    _Range._--Known only from the vicinity of Pátzcuaro, Michoacán.

    _Diagnosis._--Size large (see measurements); upper parts dark
    brown; posterior border of nasals V-shaped with apex directed
    anteriorly; frontomaxillary suture medially concave or rarely
    straight; interparietal subcircular; basisphenoid wide; tympanic
    bullae large.

    _Comparisons._--From _Liomys irroratus alleni_, _acutus_ differs
    as follows: Color slightly darker brown on upper parts; size
    slightly less; posterior border of nasals V-shaped rather than
    truncate; frontomaxillary suture medially concave or straight
    instead of convex; interparietal subcircular (anterior border)
    rather than triangular; basisphenoid broader; tympanic bullae
    larger and more inflated. From _Liomys irroratus jaliscensis_
    (topotypes), _acutus_ differs as follows: Color slightly darker
    brown on upper parts; size larger, without overlap, in external
    measurements and in basilar length, length of nasals and mastoid
    breadth; posterior border of nasals V-shaped rather than almost
    truncate; frontomaxillary suture medially concave or straight
    rather than convex; interparietal subcircular rather than
    quadrilateral; basisphenoid wider; tympanic bullae larger. From
    _Liomys irroratus pullus_, _acutus_ differs in longer body,
    shorter tail, slightly longer hind foot; all of upper parts, and
    especially upper side of tail, more brownish and less blackish;
    posterior border of nasals and frontomaxillary suture differing
    in same way as from _alleni_; interorbital region narrower in
    relation to length of skull; over-all length of skull greater;
    interparietal anteroposteriorly longer; tympanic bullae more
    inflated.

[Illustration: FIGS. 4-6. Three views of the skull of the type specimen
of _Liomys irroratus acutus_. × 1.]

_Remarks._--This relatively large, dark-colored, spiny pocket mouse of
east-central Michoacán differs from its geographic neighbors in V-shape
of posterior border of nasals, semicircular shape of interparietal,
medially concave maxillofrontal suture, wide basisphenoid and larger
tympanic bullae. The latter character is not constant. Intergradation
with _L. i. alleni_ is shown by specimens from Querendaro in which the
shape of the interparietal is exactly intermediate between those of
topotypes of the two subspecies and also in that the basisphenoid is
wider than in _acutus_ but narrower than in _alleni_. Intergradation
with _L. i. jaliscensis_ is shown, by specimen No. 120275 (U. S. N. M.)
from Zamora, in shape of posterior end of nasals, direction of
maxillofrontal suture, and shape of interparietal. In each of these
features the specimen from Zamora is almost exactly intermediate between
_acutus_ and _jaliscensis_. In large size of tympanic bullae and wider
basisphenoid the specimen agrees with _acutus_, but otherwise is nearly
as small as _jaliscensis_ to which it is here referred. Actually the
specimen could, with almost equal propriety, be referred to either
subspecies.

    _Measurements._--The measurements of two males, Nos. 100184,
    100182, and average and extreme measurements of five females,
    are, respectively, as follows: Total length, 257, 267, 244
    (230-251); length of tail, 130, 128, 122 (105-129); length of
    hind foot, 32, 31, 31 (30-33); length of ear from notch, 16, 17,
    15.3 (13.0-19); weight in grams, 71.5, 65.1, 50.8 (44.8-61.8);
    greatest length of skull, 35.2, 34.9, 33.6 (32.7-34.2);
    zygomatic breadth, 17.7, 17.5, 16.5 (16.1-17.1); interorbital
    breadth, 8.4, 8.1, 7.8 (7.5-8.0); length of nasals, 15.1, 14.9,
    14.0 (13.3-14.5); width of braincase, 15.9, 15.1, 15.0
    (14.7-15.1); alveolar length of upper molariform tooth-row, 6.0,
    6.0, 5.6 (5.5-5.9). The measurements were taken according to the
    method of Goldman (N. Amer. Fauna, 34:10, 1911). Each of the
    specimens of which measurements are given above is adult; the
    transverse enamel fold has been obliterated in M1, is
    represented by only an isolated lake in M2 (except in one female
    where all trace of the fold has worn away) and is present in M3.

    _Specimens examined._--Total, 16, all from Michoacán, Mexico,
    and unless otherwise indicated in the University of California
    Museum of Vertebrate Zoölogy, as follows: 3 mi. NW Pátzcuaro,
    6700 ft., 1; 2 mi. W Pátzcuaro, 7700 ft., 5; 2 mi. W Pátzcuaro,
    6700 ft., 2; Pátzcuaro, 1 (U. S. Nat. Mus.); 5 mi. S Pátzcuaro,
    7800 ft., 7.

       *       *       *       *       *

For the loan of comparative materials we are grateful to Dr. Harold E.
Anthony of the American Museum of Natural History, Mr. Stanley P. Young
and Dr. Hartley H. T. Jackson of the Biological Surveys Collection in
the United States National Museum, Dr. Charles P. Lyman of the Museum of
Comparative Zoölogy, and for assistance with the field work to the John
Simon Guggenheim Memorial Foundation and to Miss Annie M. Alexander.

  _Transmitted April 1, 1948._


                               22-3338





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